The optical angle sensors, which have been developed to a high quality in the last decades, dominate the market place today. Their advantage rests in the high speed, which is increasingly inevitable in drive technology, as well as in the matured technology.
However, optical angle sensors are sensitive with respect to dirt of all kinds and are applicable only in a limited temperature range. Moreover, there are no absolute optical rotation counters, which can do without battery or gearing mechanism for the absolute counting.
Corresponding magnetic absolute position counters indeed do not have such limitations, but are less precise, though.